1. Field of the Invention
The present invention relates to a method and apparatus for transmitting/receiving data over multiple frequency bands in a communication system having backward compatibility with the existing systems.
2. Description of the Related Art
The communication systems are evolving by modifying standards of the existing systems to provide higher-speed data services, or by simplifying the existing systems while solving implementation issues. For example, the Code Division Multiple Access (CDMA) system has evolved from CDMA 1× into EVolution Data Only (EV-DO). In the process where the evolution between systems is made in this way, a situation may occur where it is necessary to support both the communication systems before and after the evolution. Further, in this situation, in order to maximize the capacity while making the evolution, it is necessary not only to modify the system standards but also to use additional frequency bands.
FIG. 1 illustrates distribution of frequency bands of a CDMA 1× system and an EV-DO system in a communication system according to the prior art.
Referring to FIG. 1, the communication system includes a CDMA 1× system 102 and an EV-DO system 104, both of which use different resources, and further includes a CDMA 1× system-only terminal 110 supporting only the band-1 106 which is an operation frequency band of the CDMA 1× system 102, an EV-DO system-only terminal 114 supporting only the band-2 108 which is an operation frequency band of the EV-DO system 104, and a switching terminal 112 supporting both the CDMA 1× system 102 and the EV-DO system 104. That is, the CDMA 1× system 102 and the EV-DO system 104 use different frequency bands 106 and 108 independently.
The phrase ‘the switching terminal 112 supporting both the CDMA 1× system 102 and the EV-DO system 104’ means that the switching terminal 112 can switch to any one of the CDMA 1× system 102 and the EV-DO system 104 rather than simultaneously accessing the two systems 102 and 104, to receive a service therefrom.
Like the CDMA system described above, the IEEE 802.16e system can also expect its system evolution. In this case, the evolved systems can be classified into the existing IEEE 802.16e system (“legacy system”) and a system (“BC system”) having Backward Compatibility (BC) with the legacy system.
One service provider, while providing the IEEE 802.16e service using an arbitrary frequency band, can upgrade the legacy system to the BC system for the purpose of performance improvement to meet the need for capacity increase, and can also build another BC system in another arbitrary frequency band, as shown in FIGS. 2 and 3.
FIG. 2 illustrates an example of frequency bands for multiple systems having backward compatibility according to the prior art.
Referring to FIG. 2, a band-1 200 is a service frequency band of a legacy system, and a band-2 202 is a service frequency band of a BC system. In this case, while a legacy terminal 204 can make communication only over the band-1 200, a BC terminal 206 can make communication over both the band-1 200 and the band-2 202.
FIG. 3 illustrates another example of frequency bands for multiple systems having backward compatibility according to the prior art.
Referring to FIG. 3, a band-1 300 is a service frequency band of a BC1 system, and a band-2 302 is a service frequency band of a BC2 system. Similarly, while a legacy terminal 304 can perform communication only over the band-1 300, a BC terminal 306 can perform communication over both the band-1 300 and the band-2 302.
FIG. 4 illustrates an operation in which multiple Packet Data Units (PDUs) fragmented from a Service Data Unit (SDU) packet are transmitted over the same band according to the prior art. It is assumed herein that a base station 410 uses a band-1 and a band-2 as its operation frequency bands (or service frequency bands), a terminal 420 can perform transmission/reception over both the band-1 and the band-2, and the band-1 and the band-2 each can support both the legacy and BC systems.
Referring to FIG. 4, the communication system fragments one SDU 400 into a plurality of PDUs, i.e., PDU-A 402, PDU-B 404, and PDU-C 406. The PDU-A 402, PDU-B 404 and PDU-C 406 are transmitted to the terminal 420 only over the same band, i.e., over any one of the band-1 and the band-2, regardless of the supportable service. That is, the terminal 420 and the base station 410 can communicate with each other over both the band-1 and the band-2.
However, the prior art base station 410 transmits the PDU-A 402, PDU-B 404 and PDU-C 406 only over one band regardless of the supportable service, causing a waste of wireless resources.
FIG. 5 illustrates a method in which PDUs fragmented from one SDU are transmitted over different bands in multiple communication systems according to the prior art. It is assumed herein that the communication systems are IEEE 802.16e systems.
Referring to FIG. 5, a base station 502 allocates Down Link (DL) resources and Up Link (UL) resources in a DL frame and/or a UL frame using a MAP Information Element (MAP-IE). The base station 502 has a band-1 and a band-2 as its operation frequency bands, and the PDU(s) transmitted in the band-1 and the PDU(s) transmitted in the band-2 are independent of each other. A terminal 512 can transmit/receive data over both the band-1 and the band-2.
The base station 502 fragments the data (SDU) 500 to be transmitted to the terminal 512 into a PDU-A-1 506 and a PDU-A-2 510. To transmit the PDU-A-1 506 and the PDU-A-2 510 to the terminal 512, the base station 502 allocates DownLink MAPs (DL_MAPs) 504 and 508 to the band-1 and the band-2, respectively. Thereafter, the base station 502 transmits the PDU-A-1 506 over the band-1, and transmits the PDU-A-2 510 over the band-2, thereby transmitting the SDU 500 to the terminal 512.
As described above, upon receipt of a PDU(s), the prior art base station allocates resources over a band-1 and/or a band-2, and transmits the PDU over the allocated DL resource regions. In this case, the PDU transmitted in the band-1 and the PDU transmitted in the band-2 are independent of each other. Therefore, the terminal 512 cannot perceive that PDUs of a same SDU, received from the base station over different bands, belong to the same SDU, so it cannot reassemble the received PDUs.